The two were married for five years in the 1970s, having met through the Labour Party.

Ms Chapman told BBC Radio 5 Live Mr Corbyn was "totally committed, totally principled, and he's a workaholic in the nicest sense of the word".

But Ms Chapman, who is now a professor of communications at the University of Lincoln, said she had been "saddened and upset" by recent events in the Labour Party.

She said Mr Smith's policies were also radical and there was not much difference between the two in that regard.

But she highlighted Mr Smith's approach to the media and his ability to unite the Parliamentary Labour Party (PLP) as superior to that of Mr Corbyn.

"He's younger and I think he's more media savvy and I think he's more flexible about the way he would conduct the leadership, with a bigger emphasis on winning the election," she said.

"It's a question of balance. Do you put your energies on the constitution of the Labour Party, the democracy, building up the grassroots?

"What proportions of energy do you put to that, the thing Momentum is doing, and what proportion of your energy do you put towards fighting the Tories in Parliament and building up a successful Parliamentary Labour Party in their important democratic role of opposition."

Ms Chapman added: "I think the ability to unite the party and to have a longer term post-Brexit vision, I think that's something that's been missing.

"If he (Mr Corbyn) has got the vision, it's not coming across sufficiently in the public sphere, in the media coverage.

"The stakes are really high at the moment. The role of the PLP is going to be crucial, as we know, because there's going to be a lot of work with legislation as we withdraw.

"It's really important the Labour Party puts up a strong case in Parliament. I think that emphasis has to be on the PLP as well as the democracy and the grassroots."

Ms Chapman, speaking to Emma Barnett, who was hosting 5 Live Daily for the first time on the station, also questioned whether Mr Corbyn had the necessary leadership skills for such a job.

She said Mr Corbyn had only ever worked as a trade union organiser or an MP, and had no experience outside that.

"There are skills with leadership, there are management skills," she said.

"I think he could develop it but it's been a bit slow and it's been a bit chaotic.

"We're running out of time, because the longer he takes to develop it and his team, the more Labour is losing in the polls. That's the reality of it."

Ms Chapman also suggested he could be pressured into staying on as leader until a natural successor "that's acceptable to Momentum and the left emerges".

She added: "My heart and soul is still very much with what he stands for ... But one of the things about Jeremy is that he hasn't actually changed that much politically.

"That is what a lot of people admire, but that begs the question: Are the politics of the 1970s relevant to the 21st century, and to post-Brexit Britain? And the case has to be made for that in Parliament."